What is filtration?

Filtration:

It is the process by which fluid is forced out through a membrane or other barrier because of pressure
difference on the two sides of membrane. 

• Filtration at glomerular membranes of kidney that forms filtrate and urine.
• Filtration at arterial end of capillary that allows exit of fluid with nutrients out of blood vessel to reach the cells.

What is dialysis? Importance of dialysis.

Dialysis:

• It is one of the methods used to separate colloids and crystalloids from their mixture.
• The principle of dialysis is based on the fact that, crystalloid substances in solution can pass through semipermeable membrane while colloid particles cannot.
• Semipermeable membrane used in dialysis may be parchment membrane, cellophane membrane, cellulose nitrate, cellulose acetate etc. These are called dialyzing membrane (dialyzer) usually in the form of an elongated tube or of a bag.
• Dialyzing membrane acts as a sieve retaining the larger particles. Mixture of crystalloid and colloid is placed inside the tube or bag of diaylizer and then suspended in a vessel containing dialysis fluid. Dialysis fluid is prepared without the crystalloid substances which are to be separated. The crystalloid particles from the mixture will diffuse out to the dialysis fluid through the dialyzer down their concentration gradient, but colloids will retain within the dialyzer. Dialysis fluid is changed either periodically or continuously as the crystalloid particles diffuse out from the interior of the dialyzer into the surrounding dialysis fluid.

Importance of dialysis:

• It is used as artificial kidney for treatment of renal failure. In renal failure the crystalloid  uremic toxins, (e.g. urea, creatinine etc.) accumulate in blood since kidney fails to excrete them. So by the process of dialysis it is possible to remove these uremic toxins from blood, which allows the patients of renal failure to survive.
• It is used for treatment of hyperkalemia.